Why Tonight's ‘Leap Second’ Is Stressing Everybody Out

If we didn’t add an extra second to the clock, sometime a few million years from now, humans would sleep till noon. But for now, it’s a real stress on many businesses that worry their websites may crash — and Google’s trying to block it. (Photo: Getty Images)

We’re all pretty prepared for the leap days that occur every four years, but unpredictable “leap seconds” can wreak serious havoc across the globe. Experts are currently bracing for the extra beat, announced just six months ago, that will happen June 30, 2015.

Here’s how it’ll work. During an average day, the clock moves from 23:59:59 to 00:00:00 on one day to the next. However, during a day with a leap second, there is a mini-jump as time shifts from 23:59:59 to 23:59:60, before finally flipping to 00:00:00 — in this case on Wednesday, July 1.

Why do we need an extra second this year? “Earth’s rotation is gradually slowing down a bit, so leap seconds are a way to account for that,” says Daniel MacMillan, who works at NASA’s Goddard Space Flight Center in Greenbelt, Md., in a press release.

To break it down, a day is basically 86,400 seconds in length according to Coordinated Universal Time (UTC) or “atomic time” — and we live our lives based on this measure. One second’s duration is based on electromagnetic transitions in atoms of cesium (definite fodder for your next cocktail party conversation), which are very, very reliable — so much so that the cesium clock is accurate to one second in a whopping 1.4 million years.

That said, an average solar day — how long it takes Earth to spin once on its axis — is a little bit off the atomic clock at roughly 86,400.002 seconds in length. Our planet’s rotation is slowing down ever so slightly, as Earth, the moon, and the sun are engaging in a gravitational standoff; the last time the solar day clocked 86,400 seconds flat, the year was about 1820.

That teensy difference makes a difference; if those two milliseconds were added to the clock every day for a year, we’d be looking at almost an extra second of time per year. Indeed, when leap seconds first began in 1972, they were added at a rate of nearly one per year.

However, with the turn of the millennium, far fewer leap seconds have been needed. NASA tracks the length of Earth’s turns using an ultraprecise method called Very Long Baseline Interferometry, and scientists aren’t sure why we haven’t had to add a moment since 2012. Weather shifts, changes in the Earth’s core, or geological disturbances like earthquakes and volcanoes may be playing roles.

This year, though, an extra beat is finally needed again. If we didn’t add the leap second, gradually, our clock’s timing and daylight would not align.

The Sydney Morning Herald explains it well: “If they get rid of it, time as measured by global positioning systems and Coordinated Universal Time will drift apart. That means that sometime a few million years from now, humans or their descendants will sleep till noon.”

Adding a little time to the day comes with its own set of challenges, though, especially in the world of computing. As technology expands, so does the sheer amount of adjustments needed to account for an extra second.

Not preparing for the mini-leap can stir up major issues, leaving tech teams to scramble in the aftermath. In 2012, the extra second caused sites like Reddit and Gawker to briefly crash, and Qantas Airways had to cancel 400 flights due to a glitch in booking.

Google identified problems resulting from a leap second in 2005 in advance of a December 31st leap second in 2008. Explaining the issues: “What happens to write operations that happen during that second? Does email that comes in during that second get stored correctly? What about all the unforeseen problems that may come up with the massive number of systems and servers that we run? Our systems are engineered for data integrity, and some will refuse to work if their time is sufficiently ‘wrong.’”

Engineers had to work on a creative solution to the timing problem, now known as a leap smear. “We modified our internal NTP servers to gradually add a couple of milliseconds to every update, varying over a time window before the moment when the leap second actually happens,” Google site reliability engineer Christopher Pascoe explains in a blog post back in 2011. “This meant that when it became time to add an extra second at midnight, our clocks had already taken this into account, by skewing the time over the course of the day.”

Google says it’s now prepared to take action for all future leap seconds.

The stock exchange is also feeling the heat; it’s the first time firms have had to account for the bonus second during workday hours since trading went digital, where millionths of seconds count in the rapid-fire trading world.

The leap second will occur at 8 p.m. in New York City, where after-hours trading will end early. In locations like Australia, Japan, and South Korea, markets will just be opening and are preparing their clocks accordingly. According to Bloomberg Business, $3.7 billion is expected to be exchanged at that very moment.

The president of the Futures Industry Association’s division overseeing market technology, Greg Wood, compares the situation to a global “fire drill” for the stock exchange. “The system is only as strong as its weakest link,” Wood explains to Bloomberg. “There are going to be issues.”

According to the head of trading systems at the Japan Exchange Group Inc., Hiroki Kawai, the shift has markets on edge. “As systems continue to be more and more connected, it’s becoming harder and harder to predict just what the impact could be and how big,” he says.

Is there any way to eliminate this global stressor? Some are proposing leap seconds be done away with for good, in favor of some other solution. This November in Geneva, Switzerland, representatives at the 2015 World Radiocommunication Conference are expected to render a verdict on leap seconds.

This decision was delayed in 2012, as the world was pretty split on the matter. According to the BBC, experts at the International Telecommunication Union reported that the United States, Japan, Italy, Mexico, and France wanted to nix the leap second; the U.K., Germany, and Canada wanted to keep the system intact; and countries like Russia, Turkey, and Nigeria wanted to look into the issue further.

We’ll see what happens tomorrow when the global clock skips, and then in November when a decision on leap seconds is expected. Ultimately, time will tell (excuse the pun).